1. Field of the Invention
The present invention relates to a technique for driving the crawlers of a snow thrower machine by means of a stepless speed changing hydrostatic transmission (HST).
2. Related Art
A well-known, conventional technique for driving the crawlers of a snow thrower machine by means of an HST is disclosed in Japanese Provisional Publication No. 288663/89.
According to this conventional technique, output power is controlled by transmitting power from an engine to an input shaft of the HST through pulleys and a belt. The HST is disposed on an axle supporting housing and an output shaft thereof is inserted into the housing. The rotational speed of the output shaft is reduced by a gear train in the housing, which, in turn, drives the axles.
The above mentioned HST is fixed onto an outside surface of an upper portion of the housing, wherein the input and output shafts of the HST are disposed in a parallel relationship, one above the other. Additionally, bevel gears, plain gears and the like are disposed in the housing to form the reduction gear train that is connected to the output shaft. As a result, the housing must be lengthy in both the longitudinal and vertical directions and, therefore, is undesirably large.
Furthermore, there is no parking brake or parking brake incorporated into the power transmission system, so that even if the HST is in neutral, the snow thrower machine may skid, because of the idling of the crawlers on a slope or due to a leak of operating oil from a hydraulic motor within the HST.